Thursday, May 07, 2009

Trilobites From the Planet MONGO...errm...Portugal

Giant trilobites have been discovered in a rock quarry in northern Portugal.

The finding, published in the journal Geology, adds a new chapter to the story of some of the most successful creatures that ever lived, and may even challenge current specimens for the largest the planet has ever seen.

The current record holder for the largest trilobite still officially stands at the 72 centimeter (28.3 inch)-long Isotelus rex, a fossil recovered in Manitoba, Canada in the year 2000.

Last year, Artur Sa of the University of Tras-os-Montes and Alto Douro and a team of colleagues unearthed a slew of similar giants between 50 and 70 centimeters (19.7 and 27.6 inches) long in a slate quarry in Arouca, Portugal.

They also found two fossilized tail sections which they believe belonged to 90 centimeter (35.4 inch)-long animals, the biggest in the world.

"Normally trilobites in the Iberian Peninsula and throughout Spain don't get bigger than 10 centimeters (3.9 inches) long," Sa said. "In the quarry, they are normally above 30 centimeters in length."

Uber sized! 3 ft 'bites. Nice!


Giant trilobites and trilobite clusters from the Ordovician of Portugal
Juan C. Gutiérrez-Marco1, Artur A. Sá2,*, Diego C. García-Bellido1, Isabel Rábano3 and Manuel Valério4

1Departamento de Paleontología, Instituto de Geología Económica (CSIC-UCM), Facultad de Ciencias Geológicas, 28040 Madrid, Spain
2Departamento de Geologia, Universidade de Trás-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal; and Centro de Geociências da Universidade de Coimbra, 3000-272 Coimbra, Portugal
3Museo Geominero–IGME, Ríos Rosas 23, 28003 Madrid, Spain
4Centro de Interpretação Geológica de Canelas, 4450-252 Canelas, Portugal


Large quarrying surfaces of roofing slate in the Arouca Geopark (northern Portugal), formed under oxygen-depleted conditions, have yielded a unique Ordovician fossil lagerstätte that reveals new information on the social behavior of trilobites. It provides several of the world's largest trilobite specimens (some reaching 70 cm), showing evidence of possible polar gigantism in six different species, as well as numerous examples of monotaxic and polytaxic size-segregated autochthonous trilobite clusters, some of which contain as many as 1000 specimens. These reveal a very diverse social behavior, which includes temporary refuge from predation and synchronous molting and reproduction, demonstrated for the first time in five contemporary families of three different trilobite orders from a single formation.

Link to the paper.

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